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For an out-of-this-world experience, just lie down

By Kimm Groshong

Prolonged stays in space have a profound effect on the human body, which is adapted to the Earth’s gravitational pull.

In the greatly reduced gravity of space, humans experience bone and muscle loss, decreases in cardiovascular activity and a redistribution of fluids toward the upper body, among other physiological effects.

Now US scientists have confirmed what space researchers have long suspected – people on Earth can experience similar effects simply by lying around for days at a time. For the best simulation of space, they must recline on a bed tilted at a 6° angle with their head at the lower end.

Researchers from Ball State University in Muncie, Indiana, and Marquette University in Milwaukee, Wisconsin, compared records of the exercise performance of four male astronauts on the STS-78 space shuttle mission in 1996 with those of eight men who were confined to inclined beds and instructed to conduct the same activities as the astronauts over a 17-day period.

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They found similar declines in both groups in terms of their cardiorespiratory function and their ability to exercise. The amount of oxygen the men’s bodies were able to use optimally during cycling tests declined by 10.4% in the astronauts and by 6.6% in the bedrest subjects. Researchers would expect to see a loss of about 10% in this measure as a result of a decade of aging on Earth.

Todd Trappe, an exercise scientist at Ball State, says the finding could be used to help mitigate the effects on inactive people such as bedridden patients and the elderly, as well as ensuring the safety of long-term space travellers.

Spaceflight proxy

The similarity of the two groups’ results confirms the decades-long practice of using inclined bedrest as a proxy for spaceflight. “This 6° head-down tilt does appear to mimic the responses to spaceflight very well,” Trappe told New Scientist.

“By being in space and floating around, your body deteriorates and, as a result, when you return to a gravitational environment, your body is not up to the task,” he says. That’s not much of a problem when the gravitational environment astronauts are returning to is the Earth, where a team of people is always prepared to tend to their medical needs.

The problem would be much more serious on a lengthy mission to the Red Planet. “Out at Mars, no one’s around to help you out,” Trapp notes. And in the case of a mission emergency the body really needs its optimum cardiorespiratory function, which may no longer be sufficient after the long journey.

For that reason, researchers are working to improve the “exercise countermeasures” astronauts use while at the International Space Station to fight the bodily toll of microgravity.

Trappe is part of a group including scientists from NASA, the European Space Agency and the French space agency CNES that has recently completed a 60-day inclined bedrest study of women to simulate a two-month spaceflight. They tested a combination of resistance exercises and treadmill running as countermeasures.

Although the team is still compiling its results, Trappe told New Scientist&colon; “It appears that they’re very promising and provide a very significant attenuation of all the deleterious things that happen, at least to the muscle function.”